Traditional liner cementing involves delivery of cement through a liner that is hung off casing with the cement going through a cement shoe at the lower end of the liner and back around in the annular space around the suspended liner. Fluid is displaced by the advancing cement through the liner hanger. At the time of fluid displacement with cement, the seal on the liner hanger is not set and there are gaps between the anchor slips through which the displaced fluid moves. After the cement is delivered a trailing wiper plug is released to clear the liner of excess cement. The cement shoe has a check valve to prevent return of the cement. The seal on the liner hanger is then set and the liner running tool is released and pulled out of the hole. The shoe can be milled or drilled out and more hole can then be drilled and the process can be repeated.
In some situations there can be doubt that the cement is adequately distributed using this method and an alternative technique for cement placement is desired. This is particularly beneficial when a formation is particularly weak which can result in significant fluid loses due to low fracking gradients. In a top down delivery of cement the operating pressures to which the formation is exposed are far less than the traditional bottom up cementing which can be beneficial in minimizing impact on the formation and ultimately getting a higher production rate from the formation when the well is put into production.
While there has been talk in the industry of doing top down cementing as a concept there have been no disclosed tools that would successfully and reliably accomplish such a cementing method. At best, schematic drawings for the flow of cement and return flows are illustrated in discrete passages with no clear details of how such tools get reconfigured for the various positions needed to actually accomplish top down cementing. Some examples of this are U.S. Pat. No. 8,387,693 FIG. 117 and the associated discussion in one paragraph in the specification and US 2010/0155067 that mentions ports such as 44 and seal bores in a passing reference to top down cementing with little detail as to how the tool is reconfigured for running in and then cementing and no details how to accomplish any associated tasks such as rotation while cementing, setting a liner hanger and releasing a running tool or how to structure a crossover tool and reconfigure such a tool between cement placement and the need to set a liner hanger/packer after cementing.
A top down cementing tool operates with either mechanical manipulation or hydraulically with rotation of the liner during cementing enabled. A first bore is open for circulation during running in of the liner. In the hydraulic version, pressuring up on a dropped ball in the first bore opens cement packer setting ports and aligns crossover ports from the first bore to the annulus below the cementing packer and displaced fluid return ports to the annulus above the cementing packer. Pressuring up on a trailing wiper plug in the first bore opens the second bore so that pressuring on a seated ball in the second bore opens access to unsetting the cementing packer and launching the ball in the second bore for liner hanger setting and release of the running tool. The alternative embodiment gets the same result but with string manipulation for some of the realignments.
Embodiments are presented that operate hydraulically and mechanically to get the same result. In either case, rotation of the liner during cementing is enabled. Those skilled in the art will better understand additional aspects of the present invention from a review of the detailed description of the preferred embodiments and the associated drawings while recognizing that the full scope of the invention can be found in the appended claims.